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AppService isn't exposed after packaging to .msix

Miguel Rubio 0 Reputation points
2025-08-05T11:14:39.4033333+00:00

I have an Avalonia app targeting Windows desktop (thus, WinUI3 app).
From that project, I reference a UWP Runtime Component which handles calls to an AppService

Lastly, using a WAP project, I package the app into a .msix package, which declares in its manifest the AppService endpoint.

Everything works well when deploying the WAP project from Visual Studio (both in Debug and Release modes), but when I publish it using Publish -> Create app packages... and I then install it in the PC, the AppService starts to return AppUnavailable status when my test client tries to connect.

I have already checked namings are ok. What could it be?

Here there's a minimum reproducible example. Cloning it and deploying it from Visual Studio, and then installing it from its .msix package should denote that it works in the first scenario and it stops working in the second one.

Thanks a lot in advance for any help you can provide me

Developer technologies | .NET | .NET Runtime
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  1. Miguel Rubio 0 Reputation points
    2025-08-18T10:54:54.9633333+00:00

    In the .msix package the file WinRT.Host.runtimeconfig.json was missing. Check last commit on minimum reproducible example (here) for the solution to this issue

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  2. Adiba Khan 340 Reputation points Microsoft External Staff
    2025-08-25T07:29:37.95+00:00

    The problem usually happens because the AppService capability/endpoint is not properly exposed in the app manifest when packaged.

    ·         You must ensure the AppService extension is declared correctly in the Package.appxmanifest of the packaged app, not only in the project manifest.

    ·         Check that the executable attribute matches the packaged app entry point.

    ·         Verify that the uap.ExtensionCategory=”windows.appService” entry exists inside the manifest with the correct EntryPoint and AppService Name.

    ·         Sometimes, the app package build strips or modifies entries- so compare the manifest used in debugging vs. the one inside the .msix to confirm.

    Fix- Explicitly declare and verify the AppService configuration in the final packaged manifest, then rebuild and install/

     

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